With appropriate modifications to the magazine, the guide body (for guiding the driver and the fastener being driven) and the configuration of the driver, well within the skill of the worker in the art, the tool of the present invention can be used to drive various types of fasteners inclusive of nails, staples, clamp nails and the like. While not intended to be so limited, for purposes of an exemplary showing the tool of the present invention will be described in its application to the driving of nails.
Prior art workers have devised many types of manually operated fastener driving tools utilizing driving means actuated pneumatically, electro-mechanically or by internal combustion. To date, pneumatically actuated fastener driving tools are the ones most frequently encountered. While pneumatically actuated tools work well and have become quite sophisticated, they nevertheless require the presence of a compressor or the like.
There are many job sites where a source of compressed air is not normally present. This is particularly true of smaller job sites and the like. On the other hand, electricity is almost always present on such sites. As a consequence, particularly in recent years, prior art workers have directed considerable attention to electro-mechanical tools.
Some prior art electro-mechanical tools depend upon a heavy duty solenoid to do the fastener driving. In general, however, such tools are not adequate where large driving forces are required or desired. As a consequence, prior art workers have also expended considerable thought and effort in the development of electro-mechanical fastener driving tools employing one or more flywheels. Examples of such tools are taught in U.S. Pat. Nos. 4,042,036; 4,121,745; 4,204,622; and 4,298,072. Yet another example is taught in British Pat. No. 2,000 716.
It will be evident from these patents that prior art workers have devoted a great deal of time to the development of flywheel fastener driving tools. Nevertheless, such tools do present their own unique problems. For example, in tools utilizing two flywheels, it has been the practice to provide a separate electric motor for each flywheel. This adds considerably to the weight and bulk of the tool and is difficult to synchronize. Another approach is to mount one of the flywheels on the electric motor shaft and then drive the second flywheel through a series of belts or chains and pulleys. Such drives are complex, difficult to adjust and were subject to wear.
Another problem area involved means to cause one of the flywheels to move toward and away from the other. Preferably, for example, one of the flywheels is capable of shifting toward the other and into an operative position wherein its periphery is spaced from that of the stationary flywheel by a distance less than the nominal thickness of the thickest part of the driver. The same flywheel is shiftable in the opposite direction to an inoperative position wherein its periphery is spaced from that of the fixed flywheel by a distance greater than the greatest nominal thickness of the driver. Heretofore, systems to bring about this shifting of one of the flywheels with respect to the other have been cumbersome, complex and not altogether satisfactory.
Yet another area of concern has involved means for returning the driver at the end of the drive stroke to its normal, retracted position. For these purposes, prior art workers have developed complex systems of springs, pulleys and elastomeric cords. Such systems, however, have proven to be subject to wear, stretching and deterioration due to lubricants and foreign materials within the tool housing.
The present invention cures these and a number of other problems normally encountered with a flywheel tool. The flywheels are provided with a unique mounting assembly involving the use of two plate-like springs and a pair of rotatable, eccentric bearing housings. The tool of the present invention utilizes a single electric motor. So long as the electric motor is energized, the flywheels are constantly rotated in opposite directions by a gear train, regardless of the relative positions of the flywheels with respect to each other. The driver is free floating. At the end of the workstroke the driver is engaged between a powered return roller and an idler roller and is shifted through a return stroke to its normal, uppermost position, in which position it is engaged and locked until released for the next drive stroke. Other improvements include a unique driver actuator for introducing the driver between the flywheels at the initiation of a drive stroke, and means assuring that the various events in a cycle of operation of the tool can take place only in the proper sequence.